Fuel system for heating and cooling fuel

ABSTRACT

A fuel system has a fuel tank with a wall and a fuel delivery outlet through which fuel is delivered to the engine. The fuel tank has a fuel suction tube extending from the fuel delivery outlet into the fuel tank. Fuel is drawn to the engine from the fuel tank through the suction tube and the fuel delivery outlet. The fuel tank has a fuel cooling return inlet through which unused fuel warmed by the engine may be returned to the fuel tank and cooled. A fuel cooling conduit is coupled to the fuel cooling return inlet. The fuel cooling conduit has at least one fuel dispersing outlet through which fuel is dispersed onto the fuel tank wall to cool the fuel. A fuel warming return inlet is provided through which unused fuel warmed by the engine may be directed to flow adjacent the suction tube to heat the fuel being delivered through the suction tube to the engine. A shroud may also be provided to blend returning warm fuel with cooler fuel from the fuel tank that is flowing toward the suction tube.

TECHNICAL FIELD

The present invention relates to a fuel system for heating fuel, coolingfuel, or both heating and cooling fuel for the efficient operation ofinternal combustion engines.

BACKGROUND OF THE INVENTION

Engines, especially diesel engines, operate most efficiently when thefuel delivered to the engines is maintained within a desired temperaturerange. The low end of the desired range is above low fuel temperaturesat which fuel may thicken (wax). The high end of the desired temperaturerange is below high fuel temperatures at which engine power outputdeteriorates.

Fuel waxing is apt to occur during cold weather, when the fuel tank of avehicle is exposed to the environment. Under such conditions, fuel inthe fuel tank may thicken. Such thickened fuel may clog the engine fuelinlet lines. The clogging may result in compromised engine performanceor engine shutdown. The small fuel lines of electronic fuel injectorsprevalent today are especially vulnerable to such clogging.

Engine power output may deteriorate when the fuel being delivered to theengine becomes excessively warm. For example, the power output of dieselengines may decline by one horsepower for every 10° F. of fueltemperature over 100° F. Moreover, over-heated fuel may be detrimentalwhen fuel is used to cool engine equipment, such as in a heat exchangerelationship with electronic engine controls. Such over-heated fuel mayinadequately cool the engine equipment, resulting in a reduced servicelife for that equipment.

Fuel tends to become excessively heated when stored in a vehicle fueltank during very hot weather. Fuel also becomes overheated when used tocool engine equipment. As much as 80% of the fuel directed from the fueltank to the engine is returned unused (uncombusted) by the engine and isused for equipment cooling as the fuel is returned to the fuel tank. Thefuel picks up heat from equipment being cooled, which tends to increasethe temperature of the fuel.

Therefore, it is desirable to maintain the fuel delivered from the fueltank within a temperature range that minimizes problems associated withwaxing, degraded power output and inadequate engine equipment cooling.

One prior art approach uses radiators to cool the fuel. However,radiators tend to be expensive and prone to damage. Another approachuses a two fuel tank system to address the problem of hot fuel that isrecycled from the engine. The first tank receives the hot recycled fuelfor storage and gradual cooling, and the other tank receives cooled fuelfrom the first tank for delivery to the engine. This approach has adrawback in that, on very warm days, the fuel in the tanks may not cooladequately. Moreover, when the fuel level in the tanks is low, the hotfuel may not be stored in the cooling tank long enough for adequatecooling. Furthermore, these approaches do not address the problem offuel that is too cold.

U.S. Pat. No. 4,748,968 to Wolf discloses a fuel heating device in whichrelatively hot engine coolant circulates around a fuel tank suction tubeto warm fuel taken from the fuel tank. The Wolf device requires acoolant fluid circuit extending between the cooling system and the fueltank.

U.S. Pat. No. 5,042,447 to Stone discloses a thermostatically controlledfuel heater and cooler. The Stone device monitors the fuel temperatureand appropriately directs the fuel into a fuel heating heat exchangerutilizing relatively hot engine coolant for heating, or a fuel coolingheat exchanger utilizing a refrigerant for cooling. The coolant andrefrigerant of the Stone device circulate through lines which are linkedinto the engine cooling system, and the air conditioning system,respectively. Consequently, the Stone device adds to the complexity ofthese systems.

A need exists for an improved apparatus for temperature control of fuelwhich overcomes these and other disadvantages of the prior art.

SUMMARY OF THE INVENTION

It is one object of the present invention to provide an improved fuelsystem for adjusting fuel temperature of fuel utilized by an internalcombustion engine.

It is another object of the present invention to either heat fuelutilized by an engine, cool fuel utilized by an engine, or selectivelyheat or cool fuel utilized by an engine.

A secondary object of the present invention is to provide such a fuelsystem of simple construction.

Another secondary objective of this invention is to provide a fuelsystem for fuel cooling and/or heating that is concealed within a fueltank for protection against damage.

A fuel system in accordance with one aspect of the present invention hasa fuel tank with a fuel delivery outlet through which fuel is deliveredto an engine. The fuel tank has a fuel cooling return inlet throughwhich unused fuel warmed by the engine is returned to the fuel tank. Afuel cooling conduit may be coupled to the fuel cooling return inlet.The fuel cooling conduit has at least one fuel dispersing outlet throughwhich fuel is dispersed against a heat dissipation surface, such as awall of the fuel tank, to cool the fuel.

The fuel tank may have a fuel suction tube extending from the fueldelivery outlet into the fuel tank. Fuel is drawn to the engine from thefuel tank through the suction tube and the fuel delivery outlet. Thetank has a fuel warming return inlet through which unused fuel warmed bythe engine may be returned to the fuel tank. The warmed fuel may beguided by a fuel flow guide to blend with and heat fuel from the tankwhich is then delivered to the fuel delivery outlet and to the engine.Preferably, the unused warm fuel passes in heat transfer relationship tothe suction tube so as to heat the fuel in the suction tube.

In accordance with another aspect of the present invention, a shroud maybe provided over a portion of the fuel warming conduit and suction tube.The shroud defines a blending chamber in which heated fuel returningfrom the engine is blended with cooler fuel from the fuel tank. The warmfuel blend is then directed into the suction tube for delivery to theengine.

The present invention relates to the above-described objects andfeatures individually, as well as collectively. These and otherfeatures, objects and advantages of the present invention will becomeapparent with reference to the following description and drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional side elevational view of a fuel system inaccordance with one preferred embodiment of the present invention.

FIG. 2 is a cross-sectional end view of the fuel system in accordancewith one preferred embodiment of the present invention, taken along line2--2 of FIG. 1.

FIG. 3 is a cross-sectional view of a fuel warming portion of a fuelsystem in accordance with one preferred embodiment of the presentinvention, taken along line 3--3 of FIG. 1.

FIG. 4 is a cutaway perspective view of the fuel system in accordancewith one preferred embodiment of the present invention, with the outlineof a portion of a fuel tank being shown in dashed lines.

FIG. 5 is a cutaway, cross-sectional side elevational view of a fuelsystem in accordance with one preferred embodiment of the presentinvention.

FIG. 6 is a cutaway side elevational view of the fuel system inaccordance with a preferred embodiment of the present invention, showingthe provision of an optional shroud.

FIG. 7 is a cross-sectional view of one form of valve suitable for usein embodiments of the present invention.

DETAILED DESCRIPTION

As shown generally in FIG. 1, a fuel system for an engine 10 of a motorvehicle has a fuel tank 12 with a wall 14. The fuel tank 12 ispreferably cylindrical and elongated in a length dimension. The fueltank may be attached longitudinally beneath the cab or otherwise mountedto the motor vehicle (not shown). However, it is to be understood thatthe present invention is applicable to any fuel tank geometry, location,or orientation.

Fuel is delivered from the fuel tank 12 to the engine 10 through a fueldelivery outlet 16. A fuel suction tube 38 typically extends from thefuel delivery outlet 16 downwardly toward the bottom of the fuel tank12. The fuel suction tube 38 has a suction inlet 39. Fuel is drawn fromthe fuel tank 12 through the suction inlet 39 and the suction tube 38for delivery to the engine. A fuel delivery conduit 24 coupled to thefuel delivery outlet 16 carries fuel from the fuel delivery outlet 16 toan engine fuel inlet 25 of the engine. A fuel return conduit 26 isprovided for returning unused fuel from an engine fuel return outlet 27to the fuel tank 12.

The returning warmed fuel may be delivered to a fuel cooling subsystem,to a fuel warming subsystem, or selectively delivered to either thewarming subsystem or the cooling subsystem depending upon fueltemperature. In tropical or other warm climates, the fuel warmingsubsystem may be eliminated. Similarly, in arctic or other coldclimates, the cooling subsystem may be eliminated. In other climates orapplications, both warming and cooling subsystems may be included incombination with a mechanism for directing fuel between the warming andcooling subsystems depending upon the temperature of the fuel beingdelivered to the engine.

One such fuel flow directing mechanism comprises a valve 52. Valve 52preferably comprises a temperature sensitive valve which deliversreturning fuel to either a fuel cooling return inlet 18 or a fuelwarming return inlet 40. In one preferred embodiment, the fuel warmingreturn inlet 40 and the fuel delivery outlet 16 are positioned adjacenteach other. Together, they are spaced apart from the fuel cooling returninlet 18, in this case located adjacent to one end of the fuel tank 12.

In accordance with one aspect of the present invention, the fuel systemcools unused fuel that has been warmed by the engine, or engineequipment such as the electronic engine controls (not shown). Inaccordance with this aspect of the invention, a cooling subsystem isprovided to cool the fuel. In one illustrated form, such a coolingsubsystem may include a fuel cooling conduit 20 which is coupled to thefuel cooling return inlet 18. The fuel cooling conduit 20 includes anexternal fuel cooling tube 28, although tube 28 may be positioned insidethe fuel tank, and a fuel dispersion portion 30. The illustrated fueldispersion portion 30 has a fuel dispersion tube 32 with a plurality offuel dispersion outlets 22 that preferably comprise conventional spraynozzles. For maximum efficiency, the fuel dispersion tube typicallyextends along about the entire length of the tank. Also, the nozzles aretypically spaced an equal distance apart along the dispersion tube. Forexample, a 150 gallon fuel tank is typically about five and one-halffeet long. In such a case, the dispersion tube may be about five feetlong. Of course, it may be longer or shorter and need not be straight.Any number of nozzles may be used, providing that they are capable ofspraying the volume of fuel returned from the engine. For example, aDetroit Diesel Series 60 engine at idle returns about 1.1 gallons offuel per minute to the fuel tank. Therefore, if ten nozzles are used,each typically can deliver at least 0.11 gallons of fuel per minute atordinary engine operating fuel pressures. Typically, the nozzles have anidentical fuel delivery capacity, although this is not necessary. Also,the nozzles are typically oversized somewhat to have the capacity todeliver in excess of the maximum fuel that a particular engine willreturn to the fuel tank.

The fuel dispersion tube portion 32 extends along the length dimensionof the fuel tank 12 near the top of the fuel tank (FIGS. 1 and 4). Thenozzles are configured to direct fuel toward the fuel tank wall 14.Preferably, the nozzles spray the warm return fuel onto the fuel tankwall 14 near the top of the tank 12. The fuel tank wall 14 acts as aheat sink to cool the warm fuel as the fuel drains down the wall 14 tothe level of the fuel stored within the tank 12. Spraying the warm fuelonto a top portion of the wall 14 increases the cooling of the fuelbecause the heat transfer of the fuel to the fuel tank wall 14 tends toincrease as the drainage distance increases. Alternatively, the wall 14may be in the form of a heat dissipation element, such as a plate,baffle or other surface, supported within the tank 12.

This specific embodiment also has an advantage in that fuel will drainover a greater distance down the fuel tank wall 14 as the level of fuelin the fuel tank 12 decreases. This increase in fuel cooling tends tocounteract the decrease in fuel cooling associated with the shorterdwell time of fuel in the fuel tank storage when the tank fuel level islow.

In the embodiment shown in FIG. 1, the fuel dispersion portion 30 has anelongate frame or bracket 34 that supports the fuel dispersion tube 32along the length dimension of the fuel tank 12. The bracket 34 has aflange 35 that is mounted to the fuel tank wall 14, above the fueldispersion tube 32, by welding or any suitable fasteners. The bracket 34is spaced from the fuel tank wall 14 and is positioned to support thefuel dispersion tube 32 from below. The fuel dispersion tube 32 istherefore supported in close proximity to the fuel tank wall and thenozzles 22 are oriented to spray fuel upwardly onto the fuel tank wall.The sprayed fuel drains down the wall 14, unimpeded by the elongateframe 34.

It is to be understood that the fuel cooling subsystem of the presentinvention may take a variety of forms. for example, the fuel dispersiontube 32 may directly abut the fuel tank wall 14 so that warm return fuelflows directly onto the fuel tank wall for drainage. Any technique fordispersing the warm return fuel upon the fuel tank wall 14 or anotherheat dissipation surface is within the scope of this invention.

The fuel cooling tube 28 also includes a connecting tube portion 36,which, in the illustrated embodiment, extends from the fuel coolingreturn inlet 18 to the fuel dispersion tube portion 32. As seen in FIGS.1, 2 and 4, the connecting tube portion 36 extends downwardly from thefuel cooling return inlet 18 in an arcuate path, transversely across thebottom of the fuel tank 12, and upwardly along the wall 14 at theopposite side of the fuel tank. Near the top of the fuel tank 12, theconnection tube portion 36 connects with the fuel dispersion tube 32.

If the tank 12 is conventionally mounted longitudinally upon thevehicle, the fuel dispersion tube portion 32 is preferably mounted nearthe top of the outboard half of the fuel tank 12. In this way, the sprayis directed to the outboard portion of the wall 14 of the fuel tank 12.The outboard portion of the fuel tank wall 14 is typically betterexposed to the ambient air and to air flow when the vehicle is moving,thus enhancing the heat sink characteristics of the heat dissipationsurface. To further increase the cooling of the fuel, it may bedesirable to configure or treat the exterior of the fuel tank toincrease the radiative, convective, and/or conductive heat transfer fromthe fuel tank wall to the ambient environment. For instance, a polishedsilver-colored fuel tank surface provides excellent radiative heattransfer. The capacity of the fuel of the subject fuel system to coolequipment improves with the increased transfer of heat from the fueltank to the ambient.

The interior wall of the fuel tank may also be configured in a varietyof ways to improve fuel cooling. For instance, it may be desired toincrease the drainage time of the fuel down the fuel tank wall. In thiscase, a roughened wall surface may serve to slow the drainage of fuel.

The cooling subsystem of the fuel system of the present invention hasother advantages. The present cooling system is of simple construction,dispensing with the radiators and extensive coolant circuitry of theprior art. The present cooling system is also relatively invulnerable todamage in that the surrounding fuel tank wall 14 acts as shield toprotect the cooling subsystem.

In accordance with another aspect of the present invention, the fuelsystem may include a fuel warming subsystem to warm fuel being deliveredfrom the fuel tank 12 to the engine during cold conditions, to therebyminimize fuel waxing problems. As best shown in FIG. 5, such a warmingsubsystem may include a fuel warming conduit 42 connected to the fuelwarming return inlet 40 to act as a heat exchanger. Heat is transferredfrom warm fuel passing through the fuel return inlet 40 to fuel flowingtoward the engine within the suction tube 38. Suction tube 38 istypically of metal to enhance this heat transfer.

The illustrated fuel warming conduit 42 is a relatively large-diameterstraight tube that surrounds a substantial length of the straight,relatively small-diameter suction tube 38. The fuel warming conduit 42defines a warm fuel return path 43 between the suction tube 38 and thefuel warming conduit 42. The fuel warming conduit 42 has first andsecond diametrically tapering ends 44, 46 that are attached torespective end portions of the suction tube 38. The tapering ends 44, 46may be attached to the suction tube 38 in a variety of ways, includingwelds or interference fits. A fuel warming connector tube 48 extendsfrom the fuel warming return inlet 40 into an inlet aperture 49 on theproximate or first tapering end 44 of the fuel warming conduit 42. Afuel warming outlet aperture 50 is provided through the fuel warmingconduit 42 near the distal or second tapering end 46.

Thus, warm fuel returning from the engine passes through the fuelwarming return inlet 40, the fuel warming connector 48, the warm fuelreturn path 43 defined in this case between the suction tube and thefuel warming conduit 42, and the fuel warming outlet aperture 50 beforeflowing into the interior of the fuel tank 12.

As shown in FIG. 3, the cross-sectional area of the warm fuel returnpath 43 is greater than the cross-sectional area within the suction tube38. The flow rate of the returning fuel in the warm fuel return path 43is also less than the fuel flow rate in the suction tube 38, due to theengine using some of the fuel. Therefore, the velocity of the warm fuelflowing through the warm fuel return path 43 is less than the velocityof the fuel flow in the suction tube 38.

It is to be understood that these fuel flow velocities may be varied inalternative embodiments. As the cross-sectional area of the suction tube38 is increased, the suction tube 38 fuel flow velocity will decrease.This will increase the time of exposure of the cool fuel in the suctiontube 38 to the warm fuel in the warm fuel return path 43. The fuel beingdelivered to the engine would thus tend to be heated more. Allpermutations of the fuel flow rates, and suction tube and warm fuelreturn path geometries, fall within the scope of this invention.

The warm fuel return path configuration may be modified in further ways.For instance, instead of the fuel warming conduit 42 completelysurrounding a length of the suction tube 38, the fuel warming conduitmay be in the form of a helix winding around the fuel suction tube 38.Any embodiment in which the fuel warming return inlet 40 directs fuel toflow adjacent to the suction tube such that fuel warmed by the engineand returning to the fuel tank heats the fuel being delivered to theengine through the suction tube 38 falls within the scope of thisinvention.

In accordance with another aspect of the present invention, shown inFIG. 6, a shroud 54 may be provided over a portion of the fuel warmingconduit 42 and suction tube 38. The shroud 54 defines one form of a fuelblending or mixing chamber at the distal end of the suction tube 38. Theheated fuel is blended in this chamber with cooler fuel from the fueltank 12 that is about to enter the suction tube inlet 39 along a suctionpath 71. The fuel blend then moves along the suction path 71 into thesuction tube 38 for delivery to the engine. As seen in FIG. 6, theshroud 54 extends downwardly into the tank 12 from an attachmentposition on the fuel warming conduit 42 which is spaced above the fuelwarming outlet aperture 50. The end of the fuel suction tube 38 may beflush with the end of the fuel warming conduit 42.

The shroud 54 has a relatively small-diameter cylindrical attachmentportion 56 for attachment around the fuel warming conduit 42, anintermediate frustoconical portion 58 of a gradually increasing diametermoving downwardly along the shroud, and a relatively large-diametercylindrical shroud portion 60. The large cylindrical shroud portion 60extends from the frustrum portion 58 to an open base 62 located beyondthe ends of the respective fuel suction tube 38 and the fuel warmingconduit 42.

The shroud attachment portion 56 is typically welded to the fuel warmingconduit 42. However, it is to be understood that other attachmentapproaches, such as interference fits, or fasteners, such as clamps, maybe used.

An annular screen 64 extends laterally across the space between theexterior of the fuel warming conduit 42 and the interior of thecylindrical shroud portion 60. The screen 64 is attached to the fuelwarming conduit 42 at a position between the fuel outlet aperture 50 andthe end of the conduit 42. As a result, the screen 64 divides theinterior of the shroud 54 into an inner warm fuel receiving portion 66and a blending portion 68. The warm fuel receiving portion 66 includesthe frustrum portion 58 and that portion of the large cylindrical shroudportion 60 between the screen 64 and the frustrum portion 58. Theblending portion 68 includes that portion of the large cylindricalshroud portion 60 from the screen 64 to the base 62. The fuel receivingportion 66 receives the warm fuel exiting through the fuel warmingoutlet aperture 50. The warm fuel then passes through the screen 64along the warm fuel return path 43 to the blending portion 68.

The blending portion 68 defines a blending space wherein the warm fuelreturn path 43 and the suction path 71 converge. The blending spaceincludes the space within the blending portion 68 and the space in thefuel tank 12 immediately outside the open base 62 of the shroud 54.Within the blending space, a portion of the warm fuel within the warmfuel return path 43 blends into the cool fuel of the suction path 71.The blending yields a fuel blend with an intermediate temperature thatis higher than the temperature of the cool fuel in the fuel tank 12, andlower than the temperature of the warm return fuel. The fuel blend movesalong the suction path 71 and is drawn into the suction inlet 39.

The shroud frustrum portion 58 is provided with vapor apertures 70 thatprovide a second path of movement for the warm return fuel out of thefuel receiving portion 66. A preferred embodiment has four vaporapertures 70 positioned at 90° intervals about the frustrum portion 58.The vapor apertures 70 are positioned above the fuel warming conduitoutlet aperture 50. This arrangement permits fuel vapor bubbles 72,which may be present in the warm fuel returning from the engine, to riseand pass through the vapor apertures 70 and into the fuel tank 12. Thescreen 64 minimizes the risk of large fuel vapor bubbles 72 passing intothe blending chamber 68 and being drawn into the fuel suction tube 38and delivered to the engine.

Although variable, the screen 64 preferably has around one-hundredopenings per square inch. The screen 64 retards the flow of warm returnfuel between the receiving portion 66 and the blending portion 68 andenhances the escape of vapor bubbles through the vapor apertures 70. Thewarm fuel flow along the second path tends to heat the cool ambient fuelin the fuel tank 12. It is to be understood that the vapor and fuel flowapertures may be varied in size, shape, and number with equally goodresults. As a specific example, the fuel flow aperture may be about 0.31inches in diameter and each of the vapor apertures may be about 0.13inches in diameter.

The blending of the warm return fuel and the cool fuel within theblending chamber is advantageous in that warmed fuel is delivered to theengine rapidly after engine start-up. This blending chamber may belocated elsewhere in the fuel tank than at the end of a suction tube andmay be located outside of the fuel tank. The mixing of warm fuelreturning from the engine directly with fuel being delivered to theengine decreases the rate of heating of the remaining fuel stored in thefuel tank 12. The blending of warm and cool fuel also increases thesteady state temperature of the fuel being delivered to the engine.Therefore, fuel blending results in the delivery of warmer fuel to theengine, while the fuel remaining in the tank remains a little cooler.

The fuel blending aspect of the present invention can be accomplished ina variety of ways. For example, an outlet for warmed fuel returning fromthe engine may be placed adjacent a suction outlet for fuel beingdelivered to the engine. The blending of warm return fuel and cool fuelin the fuel tank may be accomplished in other ways, providing the warmreturning fuel is at least partially mixed with cooler fuel from thefuel tank being delivered to the engine.

In accordance with an aspect of one embodiment of the present invention,the fuel system has an optional valve 52 which operates to direct theflow of fuel returning from the engine between the fuel cooling returninlet 18 and the fuel warming return inlet 40. One suitable form ofvalve 52 is shown in FIG. 7. Valve 52 includes first and second warmfuel return ports 80, 82 which are coupled respectively to the fueldelivery outlet 16 and fuel delivery conduit 24. A passageway 84 betweenports 80, 82 remains open to supply fuel from the suction tube to theengine. The valve also has a warm fuel receiving port 86 for coupling tothe return fuel line 26, a warm fuel return port 88 for coupling to thewarm fuel inlet 40 and a cooling fuel port 90 for coupling to thecooling conduit 28. A temperature sensitive flow control valve 92selectively controls the flow of returning fuel between the ports 88, 90and thus the flow of fuel between the fuel warming and coolingsubsystems. The valve 92 includes a temperature responsive actuator,such as a wax pallet 94 manufactured by Robert Shaw Company of Chicago,Ill. As the fuel temperature in passageway 84 rises, the fuel begins tomelt wax in pallet 94. As the wax is heated, it expands and causes apiston 96 to shift to the left in FIG. 7. As piston 96 shifts to theleft, it engages a stem 97 which supports a valve disk 98. The stem 97is slidably mounted to a rod 100. A coil spring or other biasing element102 biases the disk 98 to the position shown in FIG. 7. In FIG. 7, acool fuel condition, warm fuel flows from port 86 through a passageway104 and to the port 88. The disk 98 substantially blocks the flow offuel to the port 90 and thus to the cooling subsystem. As the fuelwarms, the disk 98 is shifted to the left and opens the flow pathbetween ports 86 and 90 through passageway 104. Although not necessary,the illustrated valve 92 has an intermediate position where fuelsimultaneously flows between ports 86 and 88 as well as between ports 86and 90. This simultaneous flow of fuel is cut off when disk 98 isshifted to the left of port 86 in FIG. 7.

The valve 52 therefore comprises a temperature-sensitive valve whichdirects fuel to the fuel cooling return inlet 18 when the temperature ofthe fuel at the fuel delivery outlet 16 is above a first predeterminedmagnitude. The temperature-sensitive valve directs fuel to the fuelwarming return inlet 40 when the fuel temperature of the fuel at thefuel delivery outlet 16 is below a second predetermined magnitude.

In a preferred embodiment, the first predetermined magnitude is about80° F. When the fuel temperature at the fuel delivery outlet rises above80° F., the temperature-sensitive valve actuates to direct fuel to thefuel cooling return inlet 18 and thus to the fuel cooling subsystem.

The second predetermined magnitude in the preferred embodiment is about60° F. When the fuel at the fuel delivery outlet 16 falls below 60° F.,the temperature-sensitive valve directs the warm returning fuel to thefuel warming return inlet 40 and thereby to the fuel warming subsystem.Between 60° F. and 80° F., the fuel is diverted to both the fuel heatingand fuel cooling subsystems, with more of the fuel being delivered tothe cooling subsystem as fuel temperature rises, and vice versa.

The valve may take the form of a binary valve in that the entire flow ofreturn fuel may be delivered only to the fuel cooling return inlet 18 orthe fuel warming return inlet 40, depending on fuel temperature.

It is to be understood that other valves or flow diverters may be usedwith this invention. For instance, the valve may be manually activated(remotely from the cab of a vehicle or by a manual switch on the valve).Also, the valve may take the form of a solenoid operated valve which isoperated in response to sensed fuel temperature.

It is to be understood that the first and second predeterminedmagnitudes are exemplary only. These temperatures may be modified fordifferent grades of fuel, including diesel fuel, kerosene, and gasoline.The fuel system of the present invention is applicable to any type ofinternal combustion engine, but has particular applicability to dieselengines. The fuel cooling feature is also particularly applicable togasoline engines.

Again, it is to be understood that the heating and cooling aspects ofthis invention may be separately provided or provided in combination.For example, in hot climates, only fuel cooling may be necessary.

This detailed description is set forth only for purposes of illustratingexamples of the present invention and should not be considered to limitthe scope of the claims to the invention in any way. Numerous additions,substitutions, and modifications can be made to these examples withoutdeparting from the scope of the invention. I claim any and allmodifications that fall within the scope of the following claims.

I claim:
 1. A fuel system for an engine of a motor vehicle comprising:afuel tank; a fuel delivery flow path along which fuel from the fuel tankis delivered to an engine; a fuel return flow path along which unusedfuel warmed by the engine is returned to the fuel tank; and a heatexchanger in the fuel tank and in the fuel return flow path for coolingfuel returning to the fuel tank, the heat exchanger in the fuel tank andin the fuel return flow path having a heat dissipation surface withinthe fuel tank against which fuel returning along the fuel return flowpath is dispersed.
 2. A fuel system for an engine of a motor vehiclecomprising:a fuel tank having a wall, a fuel delivery outlet throughwhich fuel flows to the engine, and a fuel cooling return inlet throughwhich unused fuel warmed by the engine may be returned to the fuel tankfrom the engine; and a fuel cooling conduit coupled to the fuel coolingreturn inlet, the fuel cooling conduit having at least one fueldispersing outlet through which fuel is dispersed toward the wall tocool the fuel, and the fuel cooling conduit having a fuel dispersionportion with plural fuel dispersing outlets positioned in an upperregion of the fuel tank.
 3. A fuel system according to claim 2 in whichthe fuel tank is elongated in a length dimension, and wherein the fueldispersion portion extends along the length dimension of the fuel tank.4. A fuel system according to claim 2 in which the fuel cooling conduitcomprises a fuel cooling tube, the fuel dispersion portion comprising afuel dispersion tube portion of the fuel cooling tube, and the fueldispersing outlets comprising plural nozzles directed toward the wall.5. A fuel system according to claim 4 in which the fuel cooling returninlet is positioned in an upper region of the fuel tank at a locationspaced from the fuel delivery outlet and wherein the fuel cooling tubeincludes a connecting tube portion extending from the fuel coolingreturn inlet to the fuel dispersion tube portion, the connecting tubeportion extending downwardly from the fuel cooling return inlet,transversely across the fuel tank, and upwardly along the fuel tank to alocation spaced from the fuel cooling return inlet and to the fueldispersion tube portion, the fuel tank being elongated in a lengthdimension, and the fuel dispersion tube portion extending along thelength dimension of the fuel tank.
 6. A fuel system for an engine of amotor vehicle comprising:a fuel tank having a wall, a fuel deliveryoutlet through which fuel flows to the engine, and a fuel cooling returninlet through which unused fuel warmed by the engine may be returned tothe fuel tank from the engine; and a fuel cooling conduit coupled to thefuel cooling return inlet, the fuel cooling conduit having at least onefuel dispersing outlet oriented through which fuel is dispersed towardthe wall to cool the fuel; and a fuel suction tube extending into thefuel tank from the fuel delivery outlet, fuel being drawn to the enginefrom the fuel tank through the suction tube and the fuel deliveryoutlet, the fuel system having a fuel warming return inlet through whichunused fuel may be returned to the fuel tank from the engine, the fuelwarming return inlet directing fuel to flow adjacent to the suction tubesuch that fuel warmed by the engine and returning to the fuel tankthrough the fuel warming return inlet heats the fuel being deliveredthrough the suction tube and the fuel delivery outlet to the engine, anda valve operable to selectively direct the flow of fuel returning fromthe engine to the fuel cooling return inlet or the fuel warming returninlet.
 7. A fuel system according to claim 6 in which the fuel warmingreturn inlet is spaced from the fuel cooling return inlet.
 8. A fuelsystem according to claim 6 in which the fuel warming return inletincludes a heat exchanger which transfers heat from fuel returning tothe fuel warming return inlet to fuel passing through the suction tube.9. A fuel system according to claim 8 in which the heat exchangercomprises a fuel warming conduit coupled to the fuel warming returninlet and extending along a length of the suction tube.
 10. A fuelsystem according to claim 9 in which the fuel warming conduit surroundsthe suction tube and defines a warm fuel return path between the suctiontube and fuel warming conduit.
 11. A fuel system according to claim 10wherein fuel enters the suction tube along a suction flow path, andwherein the fuel warming conduit directs at least a portion of the warmfuel in the warm fuel return path to the suction flow path.
 12. A fuelsystem according to claim 6 in which the valve comprises a temperaturesensing valve operable to direct fuel to the fuel cooling return inletwhen the temperature of the fuel at the fuel delivery outlet is above afirst predetermined magnitude and to direct fuel to the fuel warmingreturn inlet when the fuel temperature of the fuel at the fuel deliveryoutlet is below a second predetermined magnitude which is less than thefirst predetermined magnitude.
 13. A fuel system according to claim 12wherein the first predetermined magnitude is about 80° F. and whereinthe second predetermined magnitude is about 60° F.
 14. A fuel system foran engine of a motor vehicle comprising:a fuel tank having a wall, afuel delivery outlet through which fuel flows to the engine, and a fuelwarming return inlet through which unused fuel warmed by the engine isreturned to the fuel tank from the engine; a fuel suction tube extendinginto the fuel tank from the fuel delivery outlet, the suction tubehaving a suction tube opening, fuel being drawn to the engine from thefuel tank through the suction tube opening and the fuel delivery outlet;and a warm fuel flow guide positioned to direct the flow of unused warmfuel past and in contact with at least a portion of the suction tubesuch that fuel warmed by the engine and returning to the fuel tank heatsthe fuel being delivered through the suction tube and the fuel deliveryoutlet to the engine, the warm fuel flow guide having a fuel outletaperture positioned above the suction tube opening such that bubbleforming vapor in the returning warm fuel exiting the fuel outletaperture can float upwardly away from the suction tube opening.
 15. Afuel system for an engine of a motor vehicle comprising:a fuel tankhaving a wall, a fuel delivery outlet through which fuel flows to theengine, and a fuel warming return inlet through which unused fuel warmedby the engine is returned to the fuel tank from the engine; a fuelsuction tube extending into the fuel tank from the fuel delivery outlet,the fuction tube having a suction tube inlet, fuel being drawn to theengine from the fuel tank through the suction tube inlet and suctiontube and the fuel delivery outlet; and a warm fuel flow guide positionedto direct the flow of unused warm fuel past at least a portion of thesuction tube such that fuel warmed by the engine and returning to thefuel tank heats the fuel being delivered through the suction tube andthe fuel delivery outlet to the engine, the warm fuel flow guide havinga warm fuel opening oriented to direct the returning warm fuel away fromthe direct flow path of fuel entering the suction tube inlet so as todivert vapor bubbles in the returning warm fuel away from the suctiontube inlet, the warm fuel flow guide also blending unused warm fuel withthe fuel entering the suction tube for delivery through the suction tubeto the engine.
 16. A fuel system according to claim 15 which includes ashroud into which fuel flowing through the warm fuel opening isdelivered, the shroud having a shroud, opening above the warm fuelopening.
 17. A fuel system according to claim 16, in which the shroudincludes a screen below the warm fuel opening.
 18. A fuel systemaccording to claim 2 in which plural fuel dispersion outlets aredirected toward an outbound portion of the fuel tank wall.
 19. A fuelsystem for an engine of a motor vehicle comprising:a fuel tank having awall, a fuel delivery outlet through which fuel flows to the engine, anda fuel warming return inlet through which unused fuel warmed by theengine is returned to the fuel tank from the engine; a fuel suction tubeextending into the fuel tank from the fuel delivery outlet, fuel beingdrawn to the engine from the fuel tank through the suction tube and thefuel delivery outlet; and a warm fuel flow guide positioned to directthe flow of unused warm fuel past at least a portion of the suction tubesuch that fuel warmed by the engine and returning to the fuel tank heatsthe fuel being delivered through the suction tube and the fuel deliveryoutlet to the engine, the warm fuel flow guide having a heat exchangerwhich transfers heat from fuel returning to the fuel warming returninlet to fuel passing through the suction tube, the heat exchangerhaving a fuel warming conduit coupled to the fuel warming return inletand extending along a length of the suction tube, the fuel warmingconduit surrounding the suction tube and defining a warm fuel returnflow path between the suction tube and fuel warming conduit; and thefuel warming conduit and suction tube terminating in a distal end spacedfrom the fuel delivery outlet, the system including a shroud mounted tothe distal end of the fuel warming conduit, the shroud defining a fuelmixing chamber communicating with the fuel warming conduit, the fueltank, and with the interior of the suction tube within which unused warmfuel from the fuel warming conduit is mixed with fuel from the fuel tankbeing delivered to the fuel suction tube.
 20. A fuel system for anengine of a motor vehicle comprising:a fuel tank having a wall, a fueldelivery outlet through which fuel flows to the engine, and a fuelwarming return inlet through which unused fuel warmed by the engine isreturned to the fuel tank from the engine; a fuel suction tube extendinginto the fuel tank from the fuel delivery outlet, the fuel suction tubehaving a suction tube inlet, and fuel being drawn to the engine from thefuel tank through the suction tube and the fuel delivery outlet; and afuel mixer within the fuel tank which directs and blends unused warmfuel returning to the fuel tank with fuel from the fuel tank being drawnthrough the suction tube, the fuel mixer having a barrier between thefuel warming return inlet and the suction tube inlet which prevents aportion of the unused warm fuel returning to the fuel tank from mixingwith fuel from the fuel tank being drawn through the suction tube.
 21. Afuel system for an engine of a motor vehicle comprising:a fuel tankhaving a wall, a fuel delivery outlet through which fuel flows to theengine, and a fuel cooling return inlet through which unused fuel warmedby the engine may be returned to the fuel tank from the engine; a fuelcooling tube coupled to the fuel cooling return inlet, the fuel coolingtube having a fuel dispersing tube portion with plural fuel dispersingoutlets through which fuel is dispersed toward a portion of the fueltank wall at an upper portion of the fuel tank; the fuel cooling conduitincludes a nozzle at each fuel dispersing outlet through which fuel issprayed toward the fuel tank wall; wherein the fuel tank is elongated ina length dimension and the fuel dispersing tube portion extends alongthe length dimension of the fuel tank; the fuel system also including afuel suction tube extending into the fuel tank from the fuel deliveryoutlet, fuel being drawn to the engine from the fuel tank through thesuction tube and the fuel delivery outlet, the fuel system having a fuelwarming return inlet through which unused fuel may be returned to thefuel tank from the engine, the fuel warming return inlet directing fuelto flow adjacent to the suction tube such that fuel warmed by the enginereturning through the fuel warming return inlet heats fuel beingdelivered to the engine through the fuel delivery outlet; and a valvewhich directs the flow of fuel returning from the engine between thefuel cooling return inlet and the fuel warming return inlet.
 22. A fuelsystem according to claim 21 in which the fuel warming return inletincludes a heat exchanger to transfer heat from the fuel returning tothe fuel warming return inlet to fuel passing through the suction tube.23. A fuel system according to claim 22 in which the heat exchangercomprises a fuel warming conduit surrounding the suction tube anddefining a warm fuel return path between the suction tube and fuelwarming conduit.
 24. A fuel system according to claim 21 in which thefuel cooling return inlet is spaced from the fuel delivery outlet.
 25. Afuel system according to claim 24 in which the valve comprises atemperature sensing valve operable to direct fuel to the fuel coolingreturn inlet when the temperature of the fuel at the fuel deliveryoutlet is above a first predetermined magnitude and to direct fuel tothe fuel warming return inlet when the fuel temperature of the fuel atthe fuel delivery outlet is below a second predetermined magnitude. 26.A fuel system for motor vehicles comprising:an engine of the type with afuel inlet for receiving fuel from a fuel tank for combustion by theengine and a fuel return outlet through which unused fuel warmed by theengine is returned; a fuel tank, a fuel return inlet and a fuel deliveryoutlet; an engine fuel delivery line coupling the engine fuel inlet tothe fuel delivery outlet through which fuel from the fuel tank isdelivered to the engine; a fuel return line coupling the engine returnoutlet and fuel return inlet through which unused warmed fuel from theengine is returned to the fuel tank; and a fuel flow guide supportedwithin the fuel tank in a position to blend unused warm fuel from theengine and fuel return inlet with fuel from the fuel tank beingdelivered to the fuel delivery outlet, the fuel flow guide having a warmreturn fuel tank inlet aperture through which warm return fuel the flowguide passes into the fuel, tank and an engine fuel inlet aperturethrough which fuel from the fuel tank passes into the flow guide, thefuel tank inlet aperture being directed away from the engine fuel inletaperture.
 27. A fuel system for motor vehicles comprising:an engine ofthe type with a fuel inlet for receiving fuel from a fuel tank forcombustion by the engine and a fuel return outlet through which unusedfuel warmed by the engine is returned; a fuel tank, a fuel return inletand a fuel delivery outlet; an engine fuel delivery line coupling theengine fuel inlet to the fuel delivery outlet through which fuel fromthe fuel tank is delivered to the engine; a fuel return line couplingthe engine return outlet and fuel return inlet through which unusedwarmed fuel from the engine is returned to the fuel tank; and a fuelflow guide supported within the fuel tank in a position to blend unusedwarm fuel from the engine and fuel return inlet with fuel from the fueltank being delivered to the fuel delivery outlet; the fuel flow guidehaving a fuel suction tube extending into the fuel tank from the fueldelivery outlet, the suction tube having a suction inlet, and fuel beingdelivered to the engine fuel delivery line from the fuel tank throughthe suction inlet; the fuel flow guide being positioned and shaped todirect the flow of unused warm fuel from the fuel return inlet in directheat transfer relationship to the suction tube such that fuel warmed bythe engine and returning to the fuel tank through the fuel warmingreturn inlet heats the fuel being delivered through the suction tube tothe fuel delivery outlet and to the engine; and a screen provided withinthe fuel flow guides between the fuel return inlet and the suctioninlet, the screen permitting warm return fuel to pass therethrough toblend with the fuel being delivered to the fuel delivery outlet.
 28. Afuel system for motor vehicles comprising:an engine of the type with afuel inlet for receiving fuel from a fuel tank for combustion by theengine and a fuel return outlet through which unused fuel warmed by theengine is returned; a fuel tank, a fuel return inlet and a fuel deliveryoutlet; an engine fuel delivery line coupling the engine fuel inlet tothe fuel delivery outlet through which fuel from the fuel tank isdelivered to the engine; a fuel return line coupling the engine returnoutlet and fuel return inlet through which unused warmed fuel from theengine is returned to the fuel tank; a fuel flow guide supported withinthe fuel tank in a position to blend unused warm fuel from the engineand fuel return inlet with fuel from the fuel tank being delivered tothe fuel delivery outlet, the fuel flow guide being positioned andshaped to direct the flow of unused warm fuel from the fuel return inletin heat transfer relationship to the suction tube such that fuel warmedby the engine and returning to the fuel tank through the fuel warmingreturn inlet heats the fuel being delivered through the suction tube tothe fuel delivery outlet and to the engine; a fuel suction tubeextending into the fuel tank from the fuel delivery outlet, the suctiontube having a suction inlet, and fuel being delivered to the engine fueldelivery line from the fuel tank through the suction inlet; the fuelflow guide having a fuel warming conduit surrounding a length of thesuction tube and defining a warm fuel return path, the fuel warmingconduit having a fuel warming outlet aperture, the warm fuel return pathpassing through the fuel warming outlet aperture; and a shroud coupledto the fuel warming conduit and defining a fuel blending chambercommunicating with the suction inlet, the fuel tank and the fuel warmingoutlet aperture, whereby unused warm fuel is blended with fuel from thefuel tank in the fuel blending chamber.
 29. A fuel system according toclaim 28 including a screen positioned within the shroud, between thefuel warming outlet aperture and the suction inlet, the warm fuel returnpath passing from the warming outlet aperture through the screen to thefuel blending chamber.
 30. A fuel system according to claim 29 whereinthe suction tube and the fuel warming conduit extend downwardly into thefuel tank; andthe shroud is provided with at least one vapor aperture,the vapor aperture being positioned above the fuel warming outletaperture and the screen to permit the escape of fuel vapor bubbles intothe fuel tank through the fuel warming outlet aperture.